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# Ruby 2: some new things

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Presentation on new features of, and changes

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### Ruby 2: some new things

1. 1. Ruby 2some new things David A. Black Lead Developer Cyrus Innovation @david_a_black Ruby Blind meetup April 10, 2013
2. 2. About me• Rubyist since 2000 (Pickaxe baby)• Lead Developer, Cyrus Innovation• Developer, author, trainer, speaker, event organizer• Author of The Well-Grounded Rubyist• Co-founder of Ruby Central• Chief author of scanf.rb (standard library)
3. 3. Todays topics• Lazy enumerators• Module#prepend• String#bytes and friends• Keyword arguments• Miscellaneous changes and new features
4. 4. Lazy enumeratorsWhats wrong with this code?# find the first 10 multiples of 3(0..Float::INFINITY).select {|x| x % 3 == 0 }.first(10)
5. 5. Lazy enumerators# find the first 10 multiples of 3(0..Float::INFINITY).select {|x| x % 3 == 0 }.first(10)It runs forever!
6. 6. Lazy enumerators# find the first 10 multiples of 3(0..Float::INFINITY).lazy.select {|x| x % 3 == 0 }.first(10)
7. 7. Lazy enumerators# find the first 10 multiples of 3(0..Float::INFINITY).lazy.select {|x| x % 3 == 0 }.first(10)=> [0, 3, 6, 9, 12, 15, 18, 21, 24, 27]
8. 8. Lazy enumeratorsr = 0..Float::INFINITYs = 0..Float::INFINITYr.zip(s).first(5) # runs forever
9. 9. Lazy enumeratorsr = 0..Float::INFINITYs = 0..Float::INFINITYr.lazy.zip(s).first(5)=> [[0, 0], [1, 1], [2, 2], [3, 3], [4, 4]]
10. 10. Lazy enumerators# From Ruby source documentationfib = Enumerator.new do |y| a = b = 1 loop do y << a a, b = b, a + b endendfib.zip(0..Float::INFINITY).first(5) # runs forever
11. 11. Lazy enumeratorsfib = Enumerator.new do |y| a = b = 1 loop do y << a a, b = b, a + b endend.lazyfib.zip(0..Float::INFINITY).first(5)# => [[1, 0], [1, 1], [2, 2], [3, 3], [5, 4]]
12. 12. Lazy enumerators• can be created via #lazy on an Enumerable • [1,2,3].lazy • (0..Float::INFINITY).lazy • an_enumerator.lazy (see Fibonacci example)
13. 13. Module#prependWhat will the output be? class Person def talk puts "Hello" end end module Yeller def talk super puts "I said... HELLLLLOOO!!!!" end end class Person include Yeller end david = Person.new david.talk
14. 14. Module#prependclass Person def talk puts "Hello" endendmodule Yeller def talk super puts "I said... HELLLLLOOO!!!!" endendclass Person include Yellerenddavid = Person.newdavid.talk# => Hello
15. 15. p Person.ancestors# => [Person, Yeller, Object, Kernel, BasicObject]
16. 16. Module#prependWhat will the output be? class Person def talk puts "Hello" end end module Yeller def talk super puts "I said... HELLLLLOOO!!!!" end end class Person prepend Yeller end david = Person.new david.talk
17. 17. Module#prependclass Person def talk puts "Hello" endendmodule Yeller def talk super puts "I said... HELLLLLOOO!!!!" endendclass Person prepend Yellerenddavid = Person.newdavid.talk# => Hello I said... HELLLLLOOO!!!!
18. 18. p Person.ancestors# => [Yeller, Person, Object, Kernel, BasicObject]
19. 19. Module#prepend• Puts the module *before* the receiver(class or module) in the method lookuppath• A good way to avoid messing with alias class Person def talk puts "Hello!" end end class Person alias old_talk talk def talk old_talk puts "I said... HELLLLLOOO!!!!" end end
20. 20. String#bytes/each_byte (and friends)• String#bytes, #lines, #chars, #codepoints now return arrays• #each_byte/line/char/codepoint still return enumerators• Saves you having to do #to_a when you want an array
21. 21. Keyword arguments def my_method(a, b, c: 3) p a, b, c end my_method(1, 2) # 1 2 3 my_method(1, 2, c: 4) # 1 2 4 Lets you specify a default value for a parameter, and use the parameters name in your method call
22. 22. Keyword argumentsdef my_method(a, b, *array, c: 3) p a, b, array, cendmy_method(1, 2, 3, 4, c: 5) # 1, 2, [3, 4], 5 Non-keyword arguments still work essentially the same way that they did.
23. 23. Keyword argumentsdef my_method(a, b, *array, c: 3, **others) p a, b, array, c, othersendmy_method(1, 2, 3, 4, c: 5, d: 6, e: 7) # 1, 2, [3, 4], 5, {:d=>6, :e=>7} Extra keyword arguments get passed along in the **others parameter.
24. 24. Keyword arguments def my_method(a, b, c) p a, b, c end my_method(1, 2, z: 3) # 1 2 {:z=>3} Hash-like arguments that dont correspond to a named argument get passed along as a hash.
25. 25. Keyword argumentsOrder doesnt matter: class Person attr_accessor :name, :email, :age def initialize(name: "", email: "", age: 0) self.name = name self.email = email self.age = age end end david = Person.new(email: "dblack@rubypal.com", name: "David", age: Float::INFINITY)
26. 26. Miscellaneous• %i{} and %I{}• Default encoding now UTF-8 (no need for magic comment)• Struct#to_h, nil#to_h, Hash#to_h• Kernel#Hash (like Array, Integer, Float)• const_get now parses nested constants • Object.const_get("A::B::C")• #inspect doesnt call #to_s any more
27. 27. • Questions?• Comments? David A. Black Lead Developer Cyrus Innovation @david_a_black Ruby Blind meetup April 10, 2013